Mobile communications networks

ABSTRACT

A mobile communications system comprising a radio access network having a multiplicity of network sites organised in a multi-layered hierarchy and a traffic flow management system for controlling the routing of traffic flow through the network. The management system trades resource at the various network sites against a plurality of user Quality of Service parameters to achieve required contractual levels of commitment to a multiplicity of users.

[0001] This invention is concerned with the control of resources inmobile communications systems. In particular the invention allows forthe management of the trade-off between radio resources and Quality ofService (QoS), and more particularly, the commitment which can be givento defined QoS parameters.

[0002] In mobile wireless communications systems user terminals (e.g.,mobile phones) are able to move. This means that communicationrequirements will vary from time to time and from place to place, andalso that the communication channel over which information is sent willvary in quality over time. Various techniques have been designed toallow for efficient use of the physical air interface when this occurs,including (but not limited to) handover (where the wireless link ischanged from one base site to another), macrodiversity (where a link ismaintained with two or more base sites at the same time), DynamicChannel Allocation (DCA) where the air interface resources available todifferent base sites are pooled and shared out between the sitesdynamically depending on current demand, Link Adaptation (where thechannel coding is changed in response to the channel quality) AdaptiveModulation (where the modulation is changed in response to the channelquality) and Adaptive Power Control (APC) where the transmission poweris changed in response to the channel quality. These differenttechniques all trade resource on the air interface against quality ofthe user data stream (the user Quality of Service), and therefore haveto be controlled in a coordinated manner. However, efficient control ofa system with so many variables is very difficult.

[0003] The generic definition of Quality of Service (QoS) is “Thecollective effect of service performances which determine the degree ofsatisfaction of a user of the service”. The satisfaction of the userdepends significantly on the service being considered. For example, QoSmeasures for speech would include clipping (loss of the start of speechbursts), echoes, crosstalk, distortion, acoustic noise, quantisationnoise, and overall signal to noise ratio. For a video service, the QoSparameters would include block distortion, blurring, edge busyness(distortion concentrated at the edge of objects, like edges shimmering),jerkiness, tiling or pixelation, frame freezing, or colour cycling(where colour stability is lost, and colours cycle through a range ofhues).

[0004] While there are a large number of different QoS measures whichare service dependent, it is possible at the transmission level of thesystem to map these different measures to generic QoS measures relatedto the network capabilities. These QoS measures are:

[0005] bit rate, both in terms of mean bit rate (throughput) andvariation of bit rate (burstiness);

[0006] delay, both in terms of absolute delay (network transit delay)and delay variation (jitter);

[0007] data corruption, in terms of Bit Error Rate (BER) and FrameErasure Rate (FER) (where packets are lost or dropped rather thanreceived with error).

[0008] According to the present invention there is provided a mobilecommunications system comprising a radio access network having amultiplicity of network sites, and a traffic flow management system forcontrolling the routing of traffic flows through the network, whereinthe management system is adapted to trade resource at the variousnetwork sites against a plurality of user Quality of Service parametersto achieve required contractual levels of commitment to a multiplicityof users.

[0009] The invention allows for the management of the trade-off betweenresources and QoS and, in particular, the commitment which can be givento defined QoS parameters. This enables network operators to convergetheir communication technologies by enabling the selection of the airinterface technology that will best serve the user requirementsdynamically.

[0010] By way of example in an embodiment the present invention allowsthe high level control functions of a communications system to choosebetween different air interface technologies and cell types in a costeffective manner in order to minimise resource use and the cost ofproviding the service. This is achieved by two key features: thedefinition of the commitment which is mapped between entities, and adivision of control functionality of the management system between threeseparate entities, one of which is responsible for the data flowwherever it is within the network, a second one of which is responsiblefor a specific link or network site, and the third one of which isresponsible for a specific transmission medium or air interface. Thisallows devolution of air interface specific functions to low levelentities and allows mapping of QoS parameters and commitment levels in apractical and achievable fashion.

[0011] The radio access network is preferably organised in a multi-layerhierarchy of network sites and by virtue of the present invention theupper layers of the network can specify not only the Quality of Servicethey wish to obtain, but also the reliability of the connection in termsof the lower (transport) layers' ability to maintain this quality (thecommitment), and furthermore allows the network to cost this commitment.

[0012] It is preferred to utilise an explicit trade-off between cost andreliability so that the user can choose the level of reliabilityrequired and the communication of QoS requirements to the lower layersin the form of standardised contracts which are independent of the airinterface.

[0013] In combination with the division into separate entities, theserequirements are mapped to transmission medium or air-interface specificrequirements at the low levels whilst commitment levels offered by thetransmission medium or air-interface are mapped back to the upper layersin a consistent format across different air interfaces so thatapplication level functions maintain QoS without requiring explicitdetails of the low level functionality. This allows for:

[0014] the effective management of resources between different types ofcommunications technologies and air interfaces within the same network;

[0015] costs of service for different areas and air interfaces to bereported and the optimal choice made (either to minimise cost of serviceor to maximise revenue for the network);

[0016] the practical implementation of such decision-making mechanismsin a devolved manner allowing dynamic selection of the most costeffective technology of a particular mobile at a particular time;

[0017] the convergence of telecommunications technologies expected infuture wireless communications systems.

[0018] Where the upper network layers express their QoS requirements inservice specific forms, these will be mapped in a Flow Controller (FC)forming part of the management system to the generic QoS requirements.However, usually the user application will undertake this conversion.The user could guide this conversion by given information on the qualityrequired, for example a graphical interface of tools could be used atthe application layer by users, network operators and service providersin order to specify a certain level of subjective QoS which is used toform the QoS requirements. These tools would be used by users to specifythe level of QoS required for a communications session such as anInternet connection or a video-conferencing application. These toolscould be developed for users or service providers by third parties whowould tailor users and service agents for a fee. As an alternative,service providers will be able to pre-define off-line sets of contracttypes using the most complete tools. The pre-defined contract typeswould then be provided to users as part of subscription packages. Fromthese contract types, contract instances will be derived and used onbehalf of subscribers for requests to the FC.

[0019] The commitment is a measure of the capability of the networkinfrastructure to maintain the contract as agreed and indicates theprobability that the network infrastructure will have to terminate orrenegotiate the contract.

[0020] These and other aspects of the invention will become apparentfrom the following description taken in combination with the drawings inwhich

[0021]FIG. 1 schematically shows a management system forming part of amobile communications system according to the present invention;

[0022]FIG. 2 shows the elements of the FIG. 1 management system mappedonto a radio access network organised in a multi-layered hierarchy;

[0023]FIG. 3 shows an example of the interactions involved in the FIG. 1management system in establishing a connection contract;

[0024]FIG. 4 shows a flow diagram of the operation of the resourcemanager of the FIG. 1 management system;

[0025]FIG. 5 shows a graphical representation of the effect oncommitment of increasing users in a communications system according tothe present invention;

[0026]FIGS. 6 and 7 show graphical interface of tools for use with themanagement system of FIG. 1;

[0027] As is shown in FIG. 1 the management system is composed of fourlayers. The lowermost or Communications layer comprises a plurality ofMedium Access Control (MAC) entities which as shown in FIG. 2 are mappedonto a radio access network to control the link between a users mobileand a radio cell.

[0028] Above the Communications layer the management system has aNetwork Pager which comprises groups of cooperating distributed entitiesFC (Flow Controller), CC (Connection Controller) and MRM (MediumResource Manager) together functioning as a Resource Manager (RM). Theseentities are shown in FIG. 2 mapped onto the radio network.

[0029] Above the Communications layer is a Services layer formed byvarious Service Agents (SA) and Network Agents (NA), and above that isthe Applications layer formed by the users.

[0030] By way of comparison with a management system operating accordingto the 7 layer open systems interconnection (OSI) system theCommunications Layer relates to Layer 1 (Physical) and Layer 2 (DataLink); the Networks Layer relates to Layer 3 (Network); the ServicesLayer relates to Layer 4 (Transport) and Layer 5 (Session) and Layer 6(Presentation); the Application layer relates to Layer 7 (Application).

[0031] The exact functionality of the Services layer is not the concernof this invention, but functionality in the Services layer carried outon behalf of the network operator is termed a network agent (NA).Service Agent (SA), is the name given here to functional entities in theservices layer operating on behalf of the service provider.

[0032] The Networks Layer utilises a hierarchical structure of the threeentities FC, CC and MRM which co-operate to provide resource managementfunctions. These entities are:

[0033] Flow Controller (FC): This is the highest layer, and controlsactivities within the network relating to the management of anindividual flow. A flow is a part of a communication within a call whichcan be treated separately. For example, a voice call may consists of adownlink (network to mobile terminal) flow and an uplink (mobileterminal to network) flow.

[0034] Connection Controller (CC): A CC is responsible for the operationof a flow at a particular location within the network. As a mobile movesthrough the network it may hand over to different CCs under the controlof a single FC.

[0035] Medium Resource Managers (MRM): A MRM is the lowest layer of theresource management hierarchy, and controls the allocation andmaintenance of resources for flows on the air interface of theassociated radio port (radio transceiver allowing access to thenetwork), or the physical layer of a fixed network link. Different radiotechnologies, such as cellular, satellite and cordless, have differentMRMs, which insulate the operation of CC from the details of thetransmission medium. This allows for practical resource negotiationbetween different transport mechanisms. Each MRM has a resource tablelisting resources currently allocated to that MRM, and maintains anestimate of the resources required to maintain the connections allocatedto it and the likelihood that the available resources will proveinsufficient for these connections in the future, bearing in mindchannel conditions. This allows the management system to predict thelikelihood that a contract will fail to be met should the quality of thephysical link degrade. The probability that such a failure will notoccur defines the commitment of the contract.

[0036] In a network having a multiplicity of different network sites asshown in FIG. 2 any flow would be controlled by a single FC wherever itis in the network. The FC organises handover and macrodiversity when itis informed by the CC that the quality of the current connection isdegraded. Depending upon the number of flows carried by the network, theflows may be divided between a number of FCs operating in parallel.

[0037] Each location or network site in the network would have a CC. A‘location’ could be a single base site or group of co-operating basesites. Base sites within the group would have the option of sharingresources, and the CC is the entity which is responsible for DCA.

[0038] Each CC will be associated with one or more MRMs. There will beone MRM for each different air interface or other type of transportmedia which is in use by the network in the location served by the CC.The CC is able to co-ordinate resource sharing between MRMs if that ispermitted and would allow more efficient use of the resources. Forexample, one location may have macro, micro and pico cells. A single CCwould co-ordinate these different systems at that location, but thedifferent cells would have different MRMs. The CC could decide which airinterface (ie, which cell) it was better to use. It could also, assumingthe air interfaces were comparable, decide to move radio resources fromone cell (and MRM) to another. Each MRM has control of the specificresources on that media in that area, and works autonomously usingcontrol algorithms such as link adaptation, adaptive modulation and APCto maintain the quality of the contracts assigned to it. This allowsdevolved control of air-interface specific techniques. If the MRM can nolonger maintain the quality of the connections assigned to it eventhrough the use of such algorithms, it informs the CC.

[0039]FIG. 2 shows the elements of the resource manager (RM) mapped onto a radio access network which for illustrative purposes is ahierarchial network. However the network structure does not require tobe of the hierarchial type to benefit from use of the resource manager(RM). Such networks would consist of a number of radio cells, rangingfrom small pico cells, covering a building or part of a building,through a microcell which may cover one or more city blocks, to amacrocell which would have a radius of several kilometres. Each mobileterminal will have a link with a base station. The exact configurationof this link will be subject to link control functions like powercontrol, but the actual allocation of resources at this lowest (link)level is, as detailed earlier, the responsibility of the Medium ResourceManager (MRM), with this entity arbitrating between users using aparticular link.

[0040] Within a specific area, the radio resources used by differentcells may interact with each other. As described above the ConnectionController (CC) controls this interaction, as well as having overallcontrol of links through MRMs. The CC is responsible for allocatingconnections between MRMs if the quality delivered by the existing MRMdegrades and the flow must be handed over to another MRM. The CC alsocontrols the overall allocation of radio resource to MRMs so that theresources are used as efficiently as possible.

[0041] The highest level of control is formed by the Flow Controller(FC), which is responsible for a call wherever it is on a network. TheFC moves the call between CCs, as appropriate, as the position of themobile terminal changes.

[0042] Operation of the management system which is shown in FIGS. 1 and2 is as follows. The FC receives flows from the upper layers of thesystem. The FC would give a commitment to carry a flow on the networkthrough the process of negotiating a flow contract. The flow contractgives detail of the service requirements, the required QoS, and thedesired level of commitment (ie, the probability that the network willbe able to meet the specified requirements on an ongoing basis withoutrenegotiation). From the details given in the flow contract, FC derivesa connection contract for example, as schematically illustrated in FIG.3. A connection contract states what is to be delivered by a CC to a FCfor a given connection in terms of QoS levels, where a connection is alink between a user terminal and a Base Station (BS). When the user ismobile, the flow will be handed over from BS to BS, therefore a flow isregarded as a sequence of connections. Once the connection contract hasbeen specified, the FC tenders the contract among the CCs which haveradio ports which may be able to provide coverage to the mobile. The CCswill then interrogate the MRMs of their radio ports to estimate theavailable resources and the resources which would be required to providethe requested service to the mobile. The MRMs will respond withconnection options for their particular air interface, along with alevel of commitment which is based on the available resources and thequality of the radio channel to the mobile. The CC will then choose themost suitable and cost effective options (in terms of radio resourceswhich would be required to be allocated) and make a bid back to the FCto handle the flow. It will also pass the relevant commitment level.From the received bids, the FC will select the CC that will serve theuser requirements with the lowest cost level bearing in mind thecommitment offered.

[0043] It is possible for the CC to offer more than one connectionoption with different associated costs and commitments. This allows thesystem to trade-off commitment level against cost.

[0044] The contract defines QoS requirements in terms of the threegeneric quality measures (bit rate, delay and corruption). The contractdefines each of these by setting statistical constraints over them. Forexample:

[0045] Mean is a constraint of the mean of the values. For example,bit_rate mean >9600 kb/s specifies that the mean of the bit rate mustnot be below 9600 kb/s.

[0046] Variance is a constraint on the variance of the values. Forexample bit_rate variance <0.02 means that the bit rate variance (orjitter) must not be above 0.02.

[0047] Percentile constrains a certain percentage of values. delaypercentile 80<10 means the at least 80% of values must have a delayunder 10 ms.

[0048] Frequency constrains the frequency of individual values or valuesin certain ranges. Delay Frequency 0,10)>80 means that at least 80% ofall values must lie between 0 ms (inclusive) and 10 ms (exclusive).

[0049] In addition to the QoS requirements, the contract will alsospecify any measurement intervals, etc, for the values unless these havebeen agree in advance.

[0050] Each MRM maintains a resource data base, eg a table, which logsdetails of the resources used, the services which occupy them, and thechannel quality for each available resource. The MRM uses thisinformation to calculate resource availability, and to estimate theresources which would be required to service a connection.

[0051] If the quality of the link to the mobile falls, the MRM will takeaction as necessary to allocate further resources to the mobile andupdate its resource estimates. If the link can no longer be maintainedwith the available resources, the MRM will inform the CC, which will inturn renegotiate its contract with the FC. The FC then has the optionof:

[0052] Adjusting its contract with the current CC, for example byreducing the required commitment or quality of service, or using moreresources at a higher cost

[0053] Re-tendering amongst different CC, which would result in ahandover to a different radio port which could now provide theconnection at lower cost. The re-tendering could take place with thesame or different service requirements.

[0054] Terminating the call. The later option is only likely to be takenif re-tendering using the same or different options fails to obtain asuitable contract.

[0055] Looking at a specific scenario in terms of a user, at any giventime the network will be supporting a plurality of users each havingtheir own contract with their supplier. It is probable that eachcontract is different in terms of financial amount and therefore eachoffers different bands of service quality. Therefore a specific userwith his specific contract may, during the course of a specifictelephone call, find that the system is providing a performance levelthat is no longer optimal but in fact approaching a limit of some formdue to the competing demands of the multiplicity of other users. In thiscase the management system instantaneously re-negotiates the contractfor the specific user, essentially to say that if he is prepared to paymore money for this particular phone call the system will improve thelevel of service back toward optimal. The user does this utilisinggraphical interface tools for example as described with reference toFIGS. 6 and 7. If the user decides that he does want this upgradeimmediately or has previously authorised such upgrades then it will beimmediately provided by the management system. However, this in turnwill mean that some or perhaps many of the multiplicity of other userswill suffer some form of reduction in their quality of service, even tothe extent of being cut off. In turn these users will be offeredre-negotiated contracts. As the management system re-negotiates themultiplicity of contracts more or less simultaneously some users willrefuse to accept a more expensive option than what is being deliveredand in some cases this will result in users being cut off. There willalso be some contracts which enable the management system to terminatethe call in the event of the quality of the service falling below apredetermined level.

[0056] A main function of the management system is to provide apractical method to enable network operators to converge theircommunication technologies by enabling the flow controller (FC) toselect the technology that will best serve the user requirementsdynamically. In particular, it allows the high level control functionsto chose between different air interface technologies and cell types ina cost effective manner in order to minimise resource use and the costof providing the service. The division of the management functionsbetween an FC, which is responsible for the flow wherever it is withinthe network, a CC, which is responsible for a specific link, and an MRM,which is responsible for a specific air interface, allows the devolutionof air interface specific functions to low level entities. Thus itallows mapping of QoS parameters and commitment levels in a practicaland achievable fashion.

[0057]FIG. 3 shows an example of the interactions between the ResourceManager entities for the establishment of a connection. In this example,a user is setting up a connection for a voice call in the centre of acity. The network which the user has subscribed to has a number ofoptions for providing a radio link to the user. The link could beprovided by a low power, short range pico cell, a higher power microcell covering the neighbouring city blocks, or a larger macro cellcovering that part of the city. It is also possible that the network mayuse satellite access as well. In the example, the network agent (NA)sends a request for a voice call to the network's FC which will controlthat call. The network agent (NA) will create a different contractrequest for each flow within the call. In a voice call, there would beone flow from the user to the network infrastructure, and one flow fromthe infrastructure to the user. Based on predictions, the FC calculateswhich CCs are in a position to serve the call, and tenders the contractto each of them. In this case, CC1 and CC3 are local micro cells, CC4 isa macro cell, and CC2 is a local pico cell. Each of these CCs calculatesthe cost of serving the contract on the commitment they can offer. Thepico cell CC offers a low cost since the resources available in a smallcell are smaller. However, the size of the cell means that commitment islikely to be lower. In this example, the user is more interested in lowcost than high commitment, and CC2 is chosen for the call. CC1, CC3 andCC4 are informed that they have been unsuccessful, and thecommunications commence using CC2.

[0058] The operation of the management system is shown in more detail inFIG. 4. The flow controller (FC) receives a call request from the corenetwork, or from a call control entity. This call request will contain aflow contract, specifying the traffic to be carried and the qualitywhich must be maintained. When the call is complete, the flow controller(FC) will report to the call control entity the fact that the call hasended, as well as the quality which was achieved optionally, the FC mayreport to the call control entity that it will not be possible tomaintain quality, allowing the call control entity the option ofblocking the call (for a new call) or seeking an alternative network forthe call.

[0059] Contracts passed to the flow controller (FC) are specified interms of

[0060] Bit rate: the minimum bit rate to be offered.

[0061] BER: a maximum BER acceptable by the service.

[0062] Delay: the maximum delay tolerated by the service.

[0063] These three primary performance parameters are complemented bythree parameters which specify how rigidly the contracted parametersmust be adhered to:

[0064] Degradation Allowance: the proportion of measures which areallowed to be non-compliant with the three performance parameters over asliding window.

[0065] Sampling rate: the rate at which measures are performed.

[0066] Monitoring Period: the length of the sliding window.

[0067] It is not necessary for these parameters to define fixed bounds.It is also possible to define a multi-mode contract which defines anumber of different traffic flows and qualities to be maintained. By sodoing, an application enables the network to vary the traffic to meetthe channel quality experienced. As a consequence more flexibility isgiven to the network which might result in lower charges. Each mode in amulti-mode contract is called a Service Mode (SM), and the FC maintainsa record of the proportion of time spent in each SM.

[0068] The FC has a resource data base, eg list, of ConnectionControllers (CC) available to it, along with a knowledge base of theirlocations, capabilities, current traffic loads, etc. In addition, the FCmaintains a list of active contracts in a Flow Monitoring Table, whichit updates to maintain a record of the achieved quality. Should qualitybegin to degrade, the FC will seek an alternative CC to carry the call,based on its knowledge of the location of the terminal and thecapabilities of relevant CCs.

[0069] The CC operates in a similar manner but is responsible only forcalls within a specified area. The CC is allocated calls by the FC, andpasses these connections to a MRM under its control on the basis oftraffic load on the MRMs and their reported quality and capacityestimates. The CC maintains a knowledge base, ie a resource data base,of its MRMs and their loading. It also receives reports from each MRM ofits expected loading, based on the connections it currently has and thechannel quality it is currently experiencing. The CC monitors thequality of the connections within its control and switches connectionsbetween MRMs, as required, to maintain their quality. The CC can alsoswitch radio resources between MRMs within its area to maintain qualitytargets.

[0070] If a MRM alerts the CC that quality cannot be met for one of itsconnections, then the CC has several alternatives:

[0071] It can hand over the connection to another MRM, as informationabout other MRM performance is maintained in the CC knowledge base.

[0072] It can release some resources from other connections by changingtheir service modes or, in the extreme situation, drop low priorityconnections.

[0073] It can change the service mode of the connection to a servicemode which requires fewer resources (this option is available only inthe case of multi-mode contracts).

[0074] If the CC cannot cope with the degradation then it alerts the FC(QoS Degradation). The CC forwards aggregate service quality measures tothe FC.

[0075] A MRM controls resources on a single link of the system, monitorsthe quality on the connection or connections allocated to it, and useslink control functions such as power control or changes in channelcoding to maintain the necessary quality. With its knowledge of thetraffic loading on the link and the current radio quality of the link,the MRM reports an estimate of available capacity to the CC so that theCC has the option of allocating more connections should resources beavailable, or of moving connections elsewhere if available resourcesfall below a specific threshold. A MRM receives low level measurementson mobile speed and direction as well as radio link quality in order tomake these predictions. A MRM can control the transmission mode—theconfiguration of the air interface with respect to channel coding,interleaving, power, etc—and may change this to maintain quality.Changing the air interface configuration will effect the remainingresources available at the MRM, and will be reported to the CCaccordingly, as will any changes in radio quality which are beyond thecapability of mode changes to deal with. The RRM is not aware of thecontract mode usage constraints specified in the multi-mode contract andis only aware of one contract operating mode at a time. The RRM isresponsible only for the change of bearer configuration and is notresponsible for the change of contract mode (CC's responsibility).

[0076] For QoS monitoring, the mobile station is usually responsible forthe monitoring of the downlinks whereas the base station is usuallyresponsible for the monitoring of the uplinks.

[0077] Quality of Service is actually communicated between the FC, CCand MRM entities in terms of commitment. Commitment is the probabilitythat the required quality will not be met over the agreed monitoringperiod and is very important to the resource manager as it allows aconsistent method of trading quality guarantees against the cost ofproviding them.

[0078] Analysis has been performed by simulation of a TETRA digitalprivate mobile radio system. The system is easily scaleable for futurecellular systems with higher bit rates, but TETRA with 10 Km cellsprovides a good example of a current system with a very diverse set ofbearers and QoS requirements which makes control difficult without themanagement system outlined herein.

[0079]FIG. 5 shows the effect of increasing the number of users ie theOffered Load in a cell for two cases, one with 5 TETRA carriers (19 userslots) and the other with 8 carriers (31 user slots). The servicechosen, 9.6 kb/s data with low delay and 1% residual BER, requiresbetween 2 and 4 slots depending on channel conditions and the bearersused. In both cases, providing a commitment of 75% limits the number ofusers to roughly half that of a commitment level of 60%. The cost for acommitment of 75′ in such a system would therefore be twice that of acommitment of 60%, for example. In general, the highest commitment isdelivered by reserving the most robust bearer all the time, althoughthis would be a costly option.

[0080]FIG. 6 illustrates a graphical interface of ‘Expert Mode’ toolswhich experienced users will be willing to use. Inexperienced users willprefer much simpler or ‘Basic Mode’ tools such as depicted by FIG. 7.These simpler tools do not have the ability to describe a detailed levelof QoS but have the advantage of being easy to manipulate.

[0081] The FIG. 6 tools could be used by service providers andexperienced users as follows:

[0082] The Application Type area enables the user to choose from asection of application types. Selecting one of them automaticallysets-up values over the quality scales of Audio, Video, Data andSynchronisation areas. The Non-Performance Properties area enables theuser to set up nonperformance constraints such as the maximum price tobe associated with the session, the performance commitment requested,the software and hardware terminal capabilities. The three middle areasAudio, Video and Data are used for specifying constraints over thevarious flows composing the session. The Synchronisation area enablesthe specification of synchronisation constraints between the video,audio and/or data flows.

[0083] The FIG. 7 tools will only enable the specification of a priceconstraint and of an overall level of quality.

1. A mobile communications system comprising a radio access networkhaving a multiplicity of network sites, and a traffic flow managementsystem for controlling the routing of traffic flows through the network,wherein the management system is adapted to trade resource at thevarious network sites against a plurality of user Quality of Serviceparameters to achieve required contractual levels of commitment to amultiplicity of users.
 2. A mobile communications system as claimed inclaim 1, wherein the management system establishes a definition ofcommitment for each traffic flow and has a Networks Layer organised as ahierarchial structure of three separate entities one of which (FC) isresponsible for flow within the network, a second one of which (CC) isresponsible for a specific link, and the third one of which (MRM) isresponsible for a specific air interface.
 3. A mobile communicationssystem as claimed in claim 2, wherein each entity comprises a resourcedata base.
 4. A mobile communications system as claimed in claim 3wherein the resource database of the FC entity has knowledge of each ofa plurality of CC entities, including their location and capabilities;the resource database of each CC entity has knowledge of each of aplurality of MRM entities, including the load of each; the resourcedatabase of each MRM entity logs details of resources used, the servicesoccupying the resources and the quality available for each resource. 5.A mobile communications system as claimed in claim 4 wherein themanagement system is arranged so that when a request for a traffic flowis received by the FC entity which will control the traffic flow, the FCentity tenders a contract to each CC entity available to serve the FCentity, each CC entry calculates the capability to serve the contractand the level of commitment which can be given and uses this to providethe FC entity with a bid for the contract, the FC entity then selectsthe most suitable bid, and therefore CC entity, to serve the terms ofthe request.